Vector Quantization Digital-to-Analog Conversion Circuit for Oversampling Converter

ABSTRACT

The present application provides a vector quantization digital-to-analog conversion circuit, for converting a digital signal to an analog signal, characterized by comprises a vector quantization circuit, configured to receive the digital signal and generate a vector quantization signal; a data weighted averaging circuit, coupled to the vector quantization circuit, comprising a plurality of data weighted averaging sub-circuits, configured to receive the vector quantization signal to generate a plurality of data weighted averaging signals; and a digital-to-analog conversion circuit, coupled to the data weighted averaging circuit, comprising a plurality of digital-to-analog conversion sub-circuits, configured to receive the data weighted averaging signal to generate the analog signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 16/154,730 filed on 2018 Oct. 9, which is a continuation applicationof international application No. PCT/CN2017/096259, filed on Aug. 7,2017.

FIELD OF THE INVENTION

The present application relates to a vector quantizationdigital-to-analog conversion circuit, and more particularly, to a vectorquantization digital-to-analog conversion circuit applied to anoversampling converter.

BACKGROUND

A converter may be roughly classified into two structures of operatingin the Nyquist Rate or operating in the Oversampling Rate (OSR), whereinthe converter operating in the oversampling rate is benefited by the twofrequency response characteristics of performing low pass filtering forsignal and performing high pass filtering for noise at the same time,and achieves a goal of separating the signal and the noise andeventually reduce the noise in baseband. With a simple exchange of afilter, the oversampling converter may realize the responsecharacteristic of performing band-pass for the signal and performingband-rejection for the noise in an intermediate frequency, so as torealize the separation of the band-pass signal and the intra-band noise,and meanwhile, finish the filtering of the band-pass signal andconversion of digital and analog signal.

No matter for an oversampling digital-to-analog converter or anoversampling analog-to-digital converter, the interior circuit must havea digital-to-analog converter. In general, the digital-to-analogconverter is configured to utilize an selected amount of interiorelements to output an analog voltage, and each element may generate thesame voltage with the same value to determine an output analog voltagevalue according to the selected amount of the interior elements, so asto realize a circuit of converting a digital quantity into an analogvoltage quantity. However, since differences in element size orcharacteristic caused by manufacturing crafts, voltage values generatedby the interior elements are not actually the same, which causes errorsof the conversion from the digital quantity into the analog quantity,and further affects accuracy and performance of the digital-to-analogconverter, and affects the oversampling converter. Therefore, theconventional technique has developed a technique which utilizes dataweighted averaging to improve declining performance caused by mismatchof the interior selected elements. However, a repetition of selectedelements of the conventional data weighted averaging technique causesthe mismatch of the elements in spectrum and generates noise voltage,which affects the signal quality and circuit performance. Accordingly,an improvement to the repetition of the selected elements of theconventional technique is to add one or more extra elements to performthe data weighted averaging so as to increase the amount of the elementsand reduce the repetition of the selected elements. However, theimprovement reduces the noise voltage caused by the mismatch of theelements but the noise voltage does not disappear, and the repetition ofthe selected elements with a specific input range still occurs, whichaffects the performance of the digital-to-analog converter.

Therefore, it is necessary to improve the conventional technique.

SUMMARY

It is therefore a primary objective of the present application toprovide a digital-to-analog converter with vector quantizationtechnique, which applies an oversampling sigma-delta (IA)digital-to-analog converter and an analog-to-digital converter toeliminate noise voltages in spectrum so as to achieve better signal tonoise ratio (SNR) and improve drawbacks of the conventional technique.

To solve the technical problems mentioned above, the present applicationprovides a vector quantization digital-to-analog conversion circuit, forconverting a digital signal to an analog signal, characterized bycomprising: a vector quantization circuit, configured to receive thedigital signal and generate a vector quantization signal; a dataweighted averaging circuit, coupled to the vector quantization circuit,comprising a plurality of data weighted averaging sub-circuits,configured to receive the vector quantization signal to generate aplurality of data weighted averaging signals; and a digital-to-analogconversion circuit, coupled to the data weighted averaging circuit,comprising a plurality of digital-to-analog conversion sub-circuits,configured to receive the data weighted averaging signal to generate theanalog signal.

Preferably, the plurality of digital-to-analog conversion sub-circuitsare configured to receive the data weighted averaging signal to generatean analog voltage and output the analog signal after summing the analogvoltage.

Preferably, an adder, coupled to the plurality of digital-to-analogconversion sub-circuits and configured to sum the analog voltage.

Preferably, the plurality of data weighted averaging sub-circuits arerespectively coupled to the plurality of digital-to-analog conversionsub-circuits; an amount of the plurality of data weighted averagingsub-circuits is identical to an amount of the plurality ofdigital-to-analog conversion sub-circuits.

Preferably, the vector quantization circuit comprises a quotientcalculator, configured to receive the digital signal to generate aquotient vector; a remainder calculator, configured to receive thedigital signal to generate a remainder; a quantization circuit, coupledto the remainder calculator, configured to receive the remainder tooutput a sorting vector; wherein after summing the quotient vector andthe sorting vector, the vector quantization signal is generated.

Preferably, the vector quantization circuit further comprises a loopcircuit, coupled to the quantization circuit, configured to receive asubtraction result of a weighted vector and the sorting vector to outputan initial vector; and an extreme circuit, coupled to the loop circuit,configured to receive the initial vector to output an updated weightedvector.

Preferably, information of allocation times of the sorting vector isrecorded in the updated weighted vector.

Preferably, the quantization circuit is configured to receive theremainder and sort the remainder according to the updated weightedvector to output the sorting vector; the sorting vector includes digitalnumbers 0 and 1, an amount of the digital number 1 of the sorting vectoris identical to the remainder and an amount of the digital number 0 ofthe sorting vector is identical to N subtracting the remainder, and N isan amount of the plurality of digital-to-analog conversion sub-circuits;the quotient vector includes N quotients.

Preferably, the loop circuit is configured to provide a delay andreceive the subtraction result of the weighted vector and the sortingvector, the subtraction result is outputted after the delay, taken asthe initial vector and transmitted to the extreme circuit.

Preferably, the updated weighted vector comprises at least a numericalvalue of zero, and the numerical value is a minimum of the updatedweighted vector.

Preferably, the extreme circuit is a minimum circuit, configured todetect a minimum of the initial vector and to subtract the minimum fromall numerical values of the initial vector to generate the updatedweighted vector.

Preferably, the quotient calculator and the remainder calculator have asame divisor, wherein the divisor and a vector dimension of the updatedweighted vector, the initial vector, the sorting vector and the quotientvector are identical; an amount of the quotient calculator and theremainder calculator is identical to an amount of the plurality ofdigital-to-analog conversion sub-circuits.

The present application further provides a vector quantizationdigital-to-analog conversion method, for converting a digital signal toan analog signal, characterized by comprising: receiving the digitalsignal and generate a vector quantization signal; receiving the vectorquantization signal to generate a plurality of data weighted averagingsignals; and receiving the data weighted averaging signal to generatethe analog signal.

The present application further provides an oversampling converter,configured to convert an analog signal to a digital signal,characterized by comprising a loop filter, configured to output a loopfiltering signal; a quantizer, configured to output a quantizationdigital signal; and a vector quantization digital-to-analog conversioncircuit, configured to output a vector quantization analog signal,wherein the vector quantization digital-to-analog conversion circuit isthe vector quantization digital-to-analog conversion circuit in claim 1;wherein the quantizer is coupled between the loop filter and the vectorquantization digital-to-analog conversion circuit.

The present application utilizes the vector quantizationdigital-to-analog conversion circuit to increase an entropy of anallocation of the digital signal, eliminate the noise voltage of theoversampling converter and increase the signal quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vector quantization digital-to-analogconversion circuit according to an embodiment of the presentapplication.

FIG. 2 is a schematic diagram of a vector quantization digital-to-analogcircuit according to an embodiment of the present application.

FIG. 3 is a schematic diagram of a signal operation of a vectorquantization digital-to-analog circuit according to an embodiment of thepresent application.

FIG. 4 is a schematic diagram of a signal operation of a vectorquantization digital-to-analog circuit according to an embodiment of thepresent application.

FIG. 5 is a schematic diagram of an oversampling analog-to-digitalconversion circuit according to an embodiment of the presentapplication.

FIG. 6 is a schematic diagram of an oversampling digital-to-analogconversion circuit according to an embodiment of the presentapplication.

FIG. 7 is another schematic diagram of a vector quantization circuitaccording to an embodiment of the present application.

FIG. 8 is a schematic diagram of a signal-to-noise ratio of anoversampling digital-to-analog conversion circuit according to anembodiment of the present application.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram of a vectorquantization digital-to-analog conversion circuit 10 according to anembodiment of the present application. The vector quantizationdigital-to-analog conversion circuit 10 may be applied to adigital-to-analog conversion circuit adopting an oversampling conversioncircuit, which allocates an input signal Vd by a vector quantizationmethod to suppress a noise voltage shaping effect, which is unable to beachieved by the conventional art, and to optimize performance of theoversampling conversion circuit. As shown in FIG. 1, the vectorquantization digital-to-analog conversion circuit 10 is configured toreceive a digital signal Vd to output an analog signal Va afterconversion, which converts the binary value of the digital signal Vdinto the analog signal Va with corresponding voltage. The vectorquantization digital-to-analog conversion circuit 10 includes a vectorquantization circuit 100, a data weighted averaging (DWA) circuit 102and a digital-to-analog converter (DAC) 104. The data weighted averagingcircuit 102 includes N data weighted averaging sub-circuits 106, and theDAC 104 includes N digital-to-analog conversion sub-circuits 108, whichare respectively coupled to the N data weighted averaging sub-circuitsto form N sub-signal paths 110. The vector quantization circuit 100receives the digital signal Vd to generate a vector Vt of N dimensions,and the vector Vt is Vt=(Vt1,Vt2, . . . ,VtN), wherein Vt1-VtN arerespectively output to the data weighted averaging sub-circuits 106,which generates V1-VN according to Vt1-VtN, and outputs V1-VN to thedigital-to-analog conversion sub-circuits 108. Then, thedigital-to-analog conversion sub-circuits 108 respectively receive V1-VNto generate the analog voltages Va1-VaN, which are summed to output theanalog signal Va.

The vector quantization circuit 100 receives the digital signal Vd andoutputs the vector Vt to the data weighted averaging circuit 102, andthe N digital signals Vt1-VtN of the vector Vt are respectively outputto the N sub-signal paths 110, the vector quantization circuit 100allocates the digital signal Vd to the vector Vt with the vectorquantization method and outputs the vector Vt to the data weightedaveraging circuit 102. In other words, the vector quantization circuit100 allocates values of the digital signal Vd to the digital signalsVt1-VtN and outputs to the N sub-signal paths 110 for operations ofcorresponding circuits.

The data weighted averaging circuit 102 receives the vector Vt, and theN data weighted averaging sub-circuits 106 respectively receive thedigital signals Vt1-VtN and output the digital signals V1-VN, whereinthe data weighted averaging sub-circuits 106 are configured toaccumulate and record the received digital signals Vt1-VtN to generatethe digital signals V1-VN by a circular pointer, so as to recordallocation times stored by the digital signals V1-VN, i.e. to record theallocation times of the respective digital-to-analog conversionsub-circuits 108.

Furthermore, the N the digital-to-analog conversion sub-circuits 108respectively receive V1-VN, and respectively generate the analogvoltages Va1-VaN, which are summed to generate the analog signal Va.Under the situation, the vector quantization digital-to-analogconversion circuit 10 allocates the digital signal Vd as the vector Vtby the N sub-signal paths 110, and outputs the N digital signals Vt1-VtNof the vector Vt of N dimensions to the corresponding N sub-signal paths110, so as to increase an entropy of the digital signal Vd and reduce aperiodicity caused by a mismatching of selected elements in thedigital-to-analog conversion sub-circuits 108 when the data weightedaveraging sub-circuits 106 are inputted with specific data values, whichreduces a noise voltage caused by the mismatching of elements, andsuppresses the noises on spectrum and improves signal-to-noise ratio(SNR).

More specifically, please refer to FIG. 2, which is a vectorquantization circuit 20 according to an embodiment of the presentapplication. The vector quantization circuit 20 may be implemented bythe vector quantization circuit 100. As shown in FIG. 2, the vectorquantization circuit 20 is configured to receive the digital signal Vdand allocate as the vector Vt for output. The vector quantizationcircuit 20 includes a quotient calculator 200, a remainder calculator202, a quantization circuit 204, a minimum circuit 206 and a loopcircuit 208, wherein the remainder calculator 202 is configured toreceive the digital signal Vd to generate a remainder R to thequantization circuit 204. The quantization circuit 204 is configured toallocate the remainder R as a sorting vector Vs according to a weightedvector Wt, and the quotient calculator 200 is connected to thequantization circuit 204 for receiving the digital signal Vd to generatea quotient Q and a quotient vector Vq. After summing the sorting vectorVs and the quotient vector Vq, the vector Vt vector-quantized from thedigital signal Vd is obtained. Notably, the vector quantization circuit20 vector-quantizes the digital signal Vd as the vector Vt, so as toaveragely allocate the allocation times of the digital-to-analogconversion sub-circuits 108 respectively. Therefore, the quotientcalculator 200 and the remainder calculator 202 have the identicalamount of N with the digital-to-analog conversion sub-circuits 108, andthe dimensions of the quotient vector Vq, the sorting vector Vs, theweighted vector Wt and the vector Vt are identical to the amount N ofthe digital-to-analog conversion sub-circuits 108.

The quotient calculator 200 is configured to calculate the quotient Q,which is the digital signal Vd divided by N, and output the quotientvector Vq (Q, Q, . . . , Q) of N dimensions, wherein the quotient vectorVq includes N quotients Q, and the remainder calculator 202 isconfigured to obtain the remainder R, which is the digital signal Vddivided by N. With operations of the minimum circuit 206 and the loopcircuit 208, the quantization circuit 204 sorts and outputs the sortingvector Vs of N dimensions, and after summing the quotient vector Vq andthe sorting vector Vs, the vector Vt is determined and output.Therefore, the vector quantization circuit 20 utilizes the quotientcalculator 200 to allocate the digital signal Vd as the quotient vectorVq with N quotients Q, and the remaining remainders R are sorted as thesorting vector Vs including amount of R of 1 by the quantization circuit204, the minimum circuit 206 and the loop circuit 208. In an embodiment,since the vector quantization circuit 20 allocates the digital signalVd, a total sum of the digital signals Vt1-VtN of the output vector Vtremains unchanged and is identical to the value of the digital signalVd.

In brief, the vector quantization circuit 20 utilizes the quantizationcircuit 204, the minimum circuit 206 and the loop circuit 208 to executethe vector quantization operation to obtain the quotient vector Vq, andallocate the obtained sorting vector Vs to the remainder R according tothe weighted vector Wt, and to generate the vector Vt after summing thesorting vector Vs and the quotient vector Vq, such that the vector Vttransmits the allocated quotient Q and the remainder R to a plurality ofsub-signal paths 210. Therefore, the present application allocates thedigital signal Vd as the vector Vt by the implementation of the vectorquantization method and transmits the vector Vt to the sub-signal paths210.

Furthermore, the weighted vector Wt stores the allocation times and theweighted information of the respective digital-to-analog conversionsub-circuits 108, the quantization circuit 204 converts the remainder Rinto the sorting vector Vs according to the values of the weightedvector Wt, which includes the same amount with the remainder R of 1 andthe amount of N—R of 0, to output the sorting vector Vs, and the sortingvector Vs is summed with the quotient vector Vq to output the vector Vt.Simultaneously, the sorting vector Vs is output to the minimum circuit206, and the loop circuit 208 performs the operation to update theweighted vector Wt. More specifically, the weighted vector Wt issubtracted from the sorting vector Vs and output to the loop circuit208. Since the sorting vector Vs is an allocation result of theremainder, and the weighted vector Wt is stored with the weightedvalues, a subtraction result of the weighted vector Wt and the sortingvector Vs represents that the weightings of the weighted vector Wt areupdated, and the loop circuit 208 receives the subtraction result andperforms a delay, and then an initial vector Vi is transmitted to theminimum circuit 206, which detects a minimum of the initial vector Vi,and offsets the values of the initial vector Vi, to return the minimumof the initial vector Vi to zero, so as to generate a new weightedvector Wt. Therefore, the larger of the values of the weighted vectorWt, the fewer of the allocation times, the higher priority of theallocated remainder R. The loop circuit 208 provides the delay to storethe weighted values, and the minimum circuit 206 subtracts the minimumof the initial vector Vi to maintain the minimum of the weighted vectorWt as zero, so as to avoid the weighted vector Wt from circumstance ofoverflow or underflow and keep accuracy of the operations.

Therefore, the vector quantization circuit 20 averagely allocates thequotient Q, allocates the remainder R with the vector quantizationmethod and allocates the input signal Vd as the vector Vt to output to Nsub-signal paths 210. Preferably, in order to allocate the input signalVd to the N sub-signal paths 210 accurately, a divisor of the quotientcalculator 200 and the remainder calculator 202 may be equal to theamount N of the sub-signal paths 210. In this way, the vectorquantization circuit 20 may convert the input signal Vd into thequantized vector Vt. Since the vector quantization method may increasethe entropy of the allocation of the remainder R, reduce a repetition ofselected elements when the sub-signal paths 210 generates the analogsignal and further eliminate the generated noise voltage to achieve banalog signal with better quantity and optimize the digital-to-analogconversion circuit.

For example, please refer to FIG. 3, which is a signal operation of avector quantization digital-to-analog conversion circuit 30 according toan embodiment of the present application. As shown in FIG. 3, the vectorquantization circuit 30 is an embodiment of the vector quantizationcircuit 20 when N=4, i.e. the vector quantization circuit 30 is coupledto 4 sets of the sub-signal paths 210, which exists the weighted vectorWt (0, 2, 0, 0.5). When the input signal Vd is 6 and input to the vectorquantization circuit 30, the quotient calculator 200 obtains the outputquotient Q of 1 and the quotient vector Vq is (1, 1, 1, 1). Theremainder calculator 202 obtains the remainder R of 2 and outputs theremainder R to the quantization circuit 204 based on the input signal Vdof 6 and the divisor of 4. Since the remainder is 2, the quantizationcircuit 204 selects two maximal numbers among the weighted vector Wt,which is (0, 2, 0, 0.5), according to the remainder R of 2, andallocates the remainder R to vector dimensions corresponding to the twomaximal numbers to generate the sorting vector Vs of (0, 1, 0, 1). Thequotient vector Vq (1, 1, 1, 1) and the sorting vector Vs (0, 1, 0, 1)are summed to obtain the output vector Vt (1, 2, 1, 2) of the vectorquantization circuit. Notably, since the vector quantization circuit 30allocates the input numbers without changing the values thereof, the sumof the values of the vector Vt is equal to the value of 6 of the inputdigital signal Vd.

Notably, after a vector allocation circuit generates the sorting vectorVs, the sorting vector Vs updates the weighted vector Wt by a cycle ofthe loop circuit, wherein after the weighted vector Wt (0, 2, 0, 0.5) issubtracted from the sorting vector Vs (0, 1, 0, 1) and input to the loopcircuit for the delay, the initial vector Vi (0, 1, 0, −0.5) isgenerated, the minimum circuit obtains the minimum −0.5 among theinitial vector Vi and all the numbers of the initial vector Vi aresubtracted from the minimum −0.5 to generate a new weighted vector Wt′(0.5, 1.5, 0.5, 0) so as to provide for the next digital signal Vd asthe input for operation. The minimum circuit 206 is utilized fordetecting the minimum −0.5 and returning the minimum of the weightedvector Wt to zero, so as to prevent the weighted vector Wt from thecircumstance of overflow or underflow and maintain the accuracy of theoperation.

In comparison, please refer to FIG. 4, which is a schematic diagram of adigital-to-analog converter 40 with the data weighted averagingtechnique according to an embodiment of the present application. Theconventional oversampling analog-to-digital converter with the dataweighted averaging technique may reduce the repetition of the selectedelements of the digital-to-analog converter 40, achieve the effect ofnoise shaping and reduce the noise voltage of the oversamplinganalog-to-digital converter. The input signal Vd of thedigital-to-analog converter 40 is first converted by a temperature meterconverter 400, then performed circular shifting by a shifter 402according to a circular indication of an indicator 404, and the shiftedtemperature metering is output to the digital-to-analog converter toindicate the operations of interior elements of the digital-to-analogconverter. With the operation of the circular shifting, the dataweighted averaging technique may averagely record and allocate theallocation times of the interior elements of the digital-to-analogconverter 406 so as to distribute the noise voltage in spectrum causedby the element mismatch and improve the signal quality, which may bededucted as 1st order mismatch shaping in mathematics. Since the effectof the mismatch shaping is related to the input data, the repetition ofthe selected elements of the digital-to-analog converter 406 is causedwhen the specific input data were input, and the repetition of theselected elements causes the noise voltage resulted by the elementmismatch in spectrum, which further affects the signal quality andcircuit performance. The said temperature meter converter may be atemperature meter encoder.

In comparison with the digital-to-analog converter 40, when the vectorquantization digital-to-analog conversion circuit 10 is applied to theoversampling analog-to-digital converter, the input signal Vd isallocated to the sub-signal paths 110, the allocation of the vectorquantization method is performed to achieve higher entropy than that ofthe interior selected elements of the digital-to-analog conversionsub-circuits 108 so as to reduce the noise voltage caused by therepetition of the interior selected elements, and achieve the effect ofnoise shaping, which cannot be achieved by the data weighted averagingmethod, and achieve better signal quality of the analog signal.

Notably, the vector quantization digital-to-analog conversion circuit ofthe present application may be applied to the oversampling converter forperforming the conversion between the digital signal and the analogsignal, wherein the oversampling converter includes a loop filter, aquantizer and a vector quantization digital-to-analog converter. Theoversampling converter is configured to utilize the loop filter, thequantizer and the vector quantization digital-to-analog converter toperform a delta-sigma modulation, which shifts the noise voltage out ofthe band, i.e. the noise voltage shaping, and further improves thesignal to noise ratio.

For example, please refer to FIG. 5, which is a schematic diagram of anoversampling analog-to-digital conversion circuit 50 according to anembodiment of the present application. As shown in FIG. 5, theoversampling analog-to-digital conversion circuit 50 is configured toreceive an analog signal Va5 so as to generate a digital output signalVd5, wherein the oversampling analog-to-digital conversion circuit 50includes a low pass filter 500, a loop filter 502, a quantizer 504 andthe vector quantization digital-to-analog conversion circuit 10, whereinthe loop filter 502 is coupled between the low pass filter 500 and thequantizer 504, the vector quantization digital-to-analog conversioncircuit 10 is coupled after the quantizer 504. The low pass filter 500is configured to receive the analog signal Va5, operate with a feedbackanalog signal, which is generated by the vector quantizationdigital-to-analog conversion circuit 10, and transmit to the loop filter502. A down converter 506 is coupled to the quantizer 504, which isconfigured to generate the output signal Vd5.

In addition, please refer to FIG. 6, which is schematic diagram of anoversampling digital-to-analog conversion circuit 60 according to anembodiment of the present application. As shown in FIG. 6, theoversampling digital-to-analog conversion circuit 60 is configured toreceive a digital signal Vd6 so as to generate an analog output signalVa6. The oversampling digital-to-analog conversion circuit 60 includesan up converter 600, the loop filter 502, the quantizer 504, the vectorquantization digital-to-analog conversion circuit 10 and the low passfilter 500, wherein the quantizer 504 is coupled between the loop filter502 and the vector quantization digital-to-analog conversion circuit 10.The up converter 600 is configured to receive the input digital signalVd6 and operate with the quantization output generated by the quantizer504, for transmitting to the loop filter 502. An output analog signal ofthe vector quantization digital-to-analog conversion circuit 10 isprocessed by the low pass filter 500 to generate the analog outputsignal Va6.

Notably, the embodiments mentioned in the above are utilized forillustrating the concept of the present application, those skilled inthe art may make modifications and alterations accordingly. For example,except for performing the allocation of the digital signal Vd as thevector Vt, a direct-current offset may be existed between the digitalsignal Vd and the vector Vt in the present application. The digitalsignal Vd may be coupled to an adder and added with a direct-currentoffset value before the digital signal Vd is input to the quotientcalculator and the remainder, such that an offset is steadily generatedby the vector Vt and the digital signal Vd. In addition, the presentapplication is not limited to utilizing the minimum circuit to achievethe idea of preventing the overflow or of the underflow, a maximumcircuit may be utilized to generate the weighted vector Wt. Please referto FIG. 7, which is a schematic diagram of a vector quantization circuit70 according to an embodiment of the present application. The vectorquantization circuit 70 is similar to the vector quantization circuit20, and the symbols remain the same of the same elements. After theinitial vector Vi is input to a maximum circuit 706, the maximum circuit706 may detect a maximum of the initial vector Vi. If the detectedmaximum is smaller than a specific value, the present application mayoffset all numbers of the initial vector Vi to adjust the maximum as thespecific value and output a weighted vector Wt to the quantizationcircuit 204 for performing the allocation of the remainder R, whichbelongs to the scope of the present application.

Please refer to FIG. 8, which is a schematic diagram of thesignal-to-noise ratio of the oversampling digital-to-analog conversioncircuit 60 according to an embodiment of the present application. Incomparison with the conventional technique, which adopts theoversampling digital-to-analog conversion circuit with the data weightedaveraging technique, where the SNR is shown in the figure, which at mostloses 16 dB. However, the SNR of the oversampling digital-to-analogconversion circuit 60 of the present application at most loses 1 dB,which can be known that the present application effectively improvesdrawbacks of the conventional technique, reduces the noise voltage ofthe oversampling converter and achieves better SNR.

As can be known from the above, the present application utilizes thevector quantization circuit to allocate the digital signal to sub-signalpaths, which not only improves the noise voltage caused by therepetition of the interior selected elements of the digital-to-analogconversion circuit with the data weighted averaging circuit, but alsohas no necessity to add redundant interior elements to thedigital-to-analog conversion circuit when an input bit number is notchanged, since a bit number of the digital-to-analog conversion circuitis related to a number of the interior elements. Besides, since an areacost of the vector quantization circuit is relatively lower than that ofthe interior elements of the digital-to-analog conversion circuit, thevector quantization circuit may effectively reduce the noise voltage ofthe oversampling converter with the area cost close to that of theconventional structure.

In summary, the present application improves the noise voltage caused bythe repetition of the interior selected elements of thedigital-to-analog conversion circuit with the data weighted averagingcircuit, and accordingly, the oversampling converter may furtherincrease the entropy of the interior elements of the analog-to-digitalconverter, so as to eliminate the noise voltage in the spectrum andachieve better SNR.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A vector quantization digital-to-analogconversion circuit, for converting a digital signal to an analog signal,characterized by comprising: a vector quantization circuit, configuredto receive the digital signal and generate a vector quantization signal;a data weighted averaging circuit, coupled to the vector quantizationcircuit, comprising a plurality of data weighted averaging sub-circuits,configured to receive the vector quantization signal to generate aplurality of data weighted averaging signals; and a digital-to-analogconversion circuit, coupled to the data weighted averaging circuit,comprising a plurality of digital-to-analog conversion sub-circuits,configured to receive the data weighted averaging signal to generate theanalog signal.
 2. The vector quantization digital-to-analog conversioncircuit of claim 1, characterized in that, the plurality ofdigital-to-analog conversion sub-circuits are configured to receive thedata weighted averaging signal to generate an analog voltage and outputthe analog signal after summing the analog voltage.
 3. The vectorquantization digital-to-analog conversion circuit of claim 2,characterized by further comprising: an adder, coupled to the pluralityof digital-to-analog conversion sub-circuits and configured to sum theanalog voltage.
 4. The vector quantization digital-to-analog conversioncircuit of claim 1, characterized in that, the plurality of dataweighted averaging sub-circuits are respectively coupled to theplurality of digital-to-analog conversion sub-circuits; an amount of theplurality of data weighted averaging sub-circuits is identical to anamount of the plurality of digital-to-analog conversion sub-circuits. 5.The vector quantization digital-to-analog conversion circuit of claim 1,characterized in that, the vector quantization circuit comprises: aquotient calculator, configured to receive the digital signal togenerate a quotient vector; a remainder calculator, configured toreceive the digital signal to generate a remainder; a quantizationcircuit, coupled to the remainder calculator, configured to receive theremainder to output a sorting vector; wherein after summing the quotientvector and the sorting vector, the vector quantization signal isgenerated.
 6. The vector quantization digital-to-analog conversioncircuit of claim 5, characterized in that, the vector quantizationcircuit further comprises: a loop circuit, coupled to the quantizationcircuit, configured to receive a subtraction result of a weighted vectorand the sorting vector to output an initial vector; and an extremecircuit, coupled to the loop circuit, configured to receive the initialvector to output an updated weighted vector.
 7. The vector quantizationdigital-to-analog conversion circuit of claim 6, characterized in that,information of allocation times of the sorting vector is recorded in theupdated weighted vector.
 8. The vector quantization digital-to-analogconversion circuit of claim 6, characterized in that, the quantizationcircuit is configured to receive the remainder and sort the remainderaccording to the updated weighted vector to output the sorting vector;the sorting vector includes digital numbers 0 and 1, an amount of thedigital number 1 of the sorting vector is identical to the remainder andan amount of the digital number 0 of the sorting vector is identical toN subtracting the remainder, and N is an amount of the plurality ofdigital-to-analog conversion sub-circuits; the quotient vector includesN quotients.
 9. The vector quantization digital-to-analog conversioncircuit of claim 6, characterized in that, the loop circuit isconfigured to provide a delay and receive the subtraction result of theweighted vector and the sorting vector, the subtraction result isoutputted after the delay, taken as the initial vector and transmittedto the extreme circuit.
 10. The vector quantization digital-to-analogconversion circuit of claim 6, the updated weighted vector comprises atleast a numerical value of zero, and the numerical value is a minimum ofthe updated weighted vector.
 11. The vector quantizationdigital-to-analog conversion circuit of claim 10, characterized in that,the extreme circuit is a minimum circuit, configured to detect a minimumof the initial vector and to subtract the minimum from all numericalvalues of the initial vector to generate the updated weighted vector.12. The vector quantization digital-to-analog conversion circuit ofclaim 6, characterized in that, the quotient calculator and theremainder calculator have a same divisor, wherein the divisor and avector dimension of the updated weighted vector, the initial vector, thesorting vector and the quotient vector are identical; an amount of thequotient calculator and the remainder calculator is identical to anamount of the plurality of digital-to-analog conversion sub-circuits.13. A vector quantization digital-to-analog conversion method, forconverting a digital signal to an analog signal, characterized bycomprising: receiving the digital signal and generate a vectorquantization signal; receiving the vector quantization signal togenerate a plurality of data weighted averaging signals; and receivingthe data weighted averaging signal to generate the analog signal.
 14. Anoversampling converter, configured to convert an analog signal to adigital signal, characterized by comprising: a loop filter, configuredto output a loop filtering signal; a quantizer, configured to output aquantization digital signal; and a vector quantization digital-to-analogconversion circuit, configured to output a vector quantization analogsignal, wherein the vector quantization digital-to-analog conversioncircuit is the vector quantization digital-to-analog conversion circuitin claim 1; wherein the quantizer is coupled between the loop filter andthe vector quantization digital-to-analog conversion circuit.
 15. Theoversampling converter of claim 14, characterized in that, theoversampling converter is an oversampling analog-to-digital converter,configured to convert the analog signal to the digital signal.
 16. Theoversampling converter of claim 15, characterized in that, theoversampling converter further comprises a low pass filter, configuredto receive the analog signal, generate a low pass analog signal,subtract from the vector quantization analog signal, and output to theloop filter.
 17. The oversampling converter of claim 15, characterizedin that, the oversampling converter further comprises a down convertercoupled to the quantizer, configured to receive the quantization digitalsignal to output the digital signal.
 18. The oversampling converter ofclaim 14, characterized in that, the oversampling converter is anoversampling digital-to-analog converter, configured to convert thedigital signal to the analog signal.
 19. The oversampling converter ofclaim 18, characterized in that, the oversampling converter furthercomprises an up converter, configured to receive the digital signal,generate an up-converted digital signal, subtract from the quantizationdigital signal, and output to the loop filter.
 20. The oversamplingconverter of claim 18, characterized in that, the oversampling converterfurther comprises a low pass filter coupled to the vector quantizationdigital-to-analog conversion circuit, configured to receive the vectorquantization analog signal to output the digital signal.